TITRATION CURVES OF ETIOLATED AND OF GREEN WHEAT SEEDLINGS REPRODUCED WITH BUFFER MIXTURES

The titration curve for the expressed juice of etiolated wheat seedlings has a pronounced inflection above pH 8.0 (fig. 4), which does not occur in the curve for fully green seedlings (fig. 5). An intermediate type of curve, linear between pH 8.5 and 11.0, is characteristic of very young seedlings just after their emergence from the ground, when, from the standpoint of chemical composition, they are partially etiolated (fig. 6). The characteristic inflection in the etiolated-seedling curve seemed due to some buffer present in maximum concentration in the absence of chlorophyll, and the change in the form of the curve during the period of seedling development appeared to be caused by a progressive diminution in the amount of this buffer as assimilation processes became established. The object of the present investigation was to identify this buffer, and to determine whether the titration curves of etiolated and of green wheat seedlings could be reproduced by varying its concentration in chemical mixtures containing it in combination with other buffer compounds known to occur in plant juices. Material